The present invention relates to new stabilized metallocene compounds of transition metals of the fourth group and a process for their preparation.
More specifically, the present invention relates to a group of metallocene complexes which includes stabilized hydrocarbyl groups, used particularly in the formation of catalysts for the (co)polymerization of xcex1-olefins and the hydrogenation of ethylenically unsaturated compounds.
It is generally known in the art that catalysts with a high activity and selectivity in the polymerization of xcex1-olefins can be obtained by combining certain organic oxyderivatives of aluminum (in particular, polymeric methylaluminoxane or MAO) with an xcex75-cyclopentadienyl compound (metallocene) of a transition metal of group four of the periodic table of elements (in the form approved by IUPAC and published in xe2x80x9cIUPAC Nomenclature of Inorganic Chemistry, Recommendations 1990xe2x80x9d, to which reference is also made hereunder). There have been numerous publications on the preparation and use of metallocenes since the eighties; among the first, reference can be made to the description of H. Sinn, W. Kaminsky, in Adv. Organomet. Chem., vol. 18 (1980), page 99 and U.S. Pat. No. 4,542,199.
More recently, catalysts of the metallocene type have been developed in the art, capable of polymerizing olefins also in the absence of organo-oxygenated compounds of aluminum and, in any case, including a lower overall quantity of metals. Said catalytic systems are normally obtained by contact and reaction of a suitable metallocene with an activator consisting of a strong Lewis acid or, more advantageously, of certain organometallic salts whose anion has a delocalized charge and is slightly coordinative, usually a fluorinated tetra aryl borane. Several catalytic systems of this type are described, for example, in the publications of R. R. Jordan in xe2x80x9cAdvances in Organometallic Chemistryxe2x80x9d, vol. 32 (1990), pages 325-387, and of X. Yang et al. in xe2x80x9cJournal of America Chemical Societyxe2x80x9d, vol. 116 (1994), page 10015, where numerous patent references on the matter, are quoted, together with a wide general survey in the field.
Further catalytic systems, in some way correlated to the preceding ones, are obtained by the reaction of metallocenes and fluoraryl aluminates, as described in international patent application WO 98/0715, which describes the enhancement of the catalytic activity. These catalysts, however, are relatively complex to prepare and are particularly unstable to air and humidity, analogously to those containing boro-anions. Moreover, they cannot be easily obtained from non-alkylated metallocene complexes.
One of the unresolved drawbacks of metallocene catalysts which do not contain aluminoxanes is the relative complexity of the process for their obtainment, as well as various problems relating to their stability. It is well known, in fact, that these catalysts can be obtained by the direct reaction of an alkyl-metallocene, such as, for example, dimethyl bis-indenyl zirconium, with a suitable salt including a boro-anion with a delocalized charge and a cation capable of extracting an alkyl group bonded to the metallocene and forming a neutral and stable molecule. The use of alkyl metallocenes, however, causes serious problems relating to the preservation and stability of these compounds, and consequently the possibility is known of obtaining equally active catalysts also starting from metallocene chlorides but using an alkyl aluminum to form, in situ, an alkyl metallocene. This latter method, however, does not allow full utilization of the metallocene compound, which is partially deactivated, and also requires the use of high quantities of aluminum in the co-catalyst, with a consequent deterioration in the dielectric properties and compatibility with food of the polymeric or hydrogenated products obtained in the presence of said catalysts.
Japanese patent application No. 11-165075 describes certain metallocene complexes of a metal of group 4 comprising two styril or oligostyril groups bonded to the metal. Such complexes are used for the catalytic hydrogenation of olefins.
The production of metallocene catalysts for the polymerization of olefins therefore seems to still have significant drawbacks, in spite of the remarkable progress made with respect to the traditional Ziegler-Natta polymerization, and there seem to be considerable margins for further improvement to meet the increasingly refined demands of industry and the market.
Studies on the structure and synthesis of bis-cyclopentadienyl-allyl complexes of metals of group 4 of the periodic table have been reported in literature, in the publication J. Organomet. Chem., vol. 14, pages 149-156, (1968). In this study, a significant instability of said allyl complexes with time, is observed.
Subsequently, Italian patent application nr. MI00A02776, of the Applicant, describes allyl-metallocene complexes of group 4, showing a significantly improved stability and performance reproducibility. The allyl-metallocene complexes described therein, however, also need particular attention during their synthesis and do not have a completely satisfactory versatility in the formation of the desired catalysts.
In the continuous attempt to satisfy the above demands with the development of innovative processes and materials, the Applicant has now found a new group of metallocene complexes with stabilizing hydrocarbyl groups in the molecule, which surprisingly allow catalytic systems to be obtained, which are stable enough to allow their transportation and storage for prolonged periods of time and which are also easy to prepare and suitable for the formation of metallocene catalysts, combined both with co-catalysts based on aluminoxanes and with co-catalysts based on ionizing ionic compounds, such as the salts of tetra-aryl boron-anions mentioned above.
A first object of the present invention therefore relates to a metallocene complex of a metal of group 4 of the periodic table, having the following formula (I): 
wherein:
M is selected from Titanium, Zirconium and Hafnium, preferably from Titanium and Zirconium, coordinatively bonded to a first xcex75-cyclopentadienyl group;
Rxe2x80x2 represents an unsaturated, hydrocarbyl group,
Rxe2x80x3 represents an optional group anionically bonded to the metal M, consisting of an organic or inorganic radical, different from cyclopentadienyl or substituted cyclopentadienyl;
the groups R1, R2, R3, R4, R5, each independently represent, an atom or radical bonded to said first xcex75-cyclopentadienyl group, selected from hydrogen or any other suitable organic or inorganic substituent of said cyclopentadienyl group;
R6 represents any other suitable organic or inorganic group, anionically bonded to the metal M;
xe2x80x9cwxe2x80x9d has the value of 0 or 1, according to whether the Rxe2x80x3 group is absent or present in formula (I);
characterized in that said Rxe2x80x2 group consists of an unsaturated oligomeric group having the following formula (II):
-(AxDyUz)RIxe2x80x83xe2x80x83(II)
wherein:
A represents any monomeric unit deriving from a vinylaromatic group polymerizable by means of anionic polymerization, having from 6 to 20 carbon atoms;
D represents any monomeric unit deriving from a conjugated diolefin polymerizable by means of anionic polymerization, having from 4 to 20 carbon atoms;
U represents any generic optional monomeric unit deriving from an unsaturated compound co-polymerizable with any of the above conjugated diolefins D or vinylaromatic compounds A;
RI represents hydrogen or a hydrocarbyl group having from 1 to 20 carbon atoms, each index xe2x80x9cxxe2x80x9d and xe2x80x9cyxe2x80x9d can be independently zero or an integer, provided the sum (x+y) is equal to or higher than 2, preferably between 2 and 50, even more preferably between 2 and 25;
xe2x80x9czxe2x80x9d can be zero or an integer ranging from 1 to 20;
with the proviso that, when R6 is a xcex75-cyclopentadienyl or substituted xcex75-cyclopentadienyl group and Rxe2x80x2 is -(Ax)RI, Rxe2x80x3 is different from -(Ax)RI.
A simple, high-yield process for the preparation of said complexes having formula (I), constitutes a second object of the invention.
Any further possible objects of the present inventions will appear evident from the following description and examples.